Most paint spray guns operate with compressed air for controlling the pattern of the atomized paint and/or for assisting paint atomization. The paint is discharged from a nozzle which is mounted adjacent to an air cap. The atomization air and/or pattern shaping air is discharged from the air cap. During spraying, there is a tendency for some paint to accumulate on the air cap and on exposed surfaces on the nozzle. Normally, such paint accumulation must be manually cleaned from the spray gun. The cleaning operation may interfere with production when an automatic spray gun on a manufacturing production line requires cleaning.
In one type of spray gun, paint is atomized by centrifugal discharge from a bell or cup which is rotated at a high speed. U.S. Pat. No. 4,275,838 discloses an automatic system for cleaning the bell. An annular shroud is mounted to normally be located behind the bell. For cleaning, a pneumatic cylinder advances the shroud to surround the bell. A single solvent nozzle is mounted in the shroud to spray solvent at the bell after the shroud is advanced. This system has the advantage of being automatic, but the disadvantage of requiring separate controls for the pneumatic cylinder and the solvent. Also, this system has not previously been adapted to an air atomization type spray guns.